Surface Expression of Basal and Englacial Features, Properties, and Processes of the Greenland Ice Sheet

Abstract

Radar‐sounding surveys measuring ice thickness in Greenland have enabled an increasingly “complete” knowledge of basal topography and glaciological processes. Where such observations are spatially limited, bed elevation has been interpolated through mass conservation or kriging. Ordinary kriging fails to resolve anisotropy in bed geometry, however, leaving complex topography misrepresented in elevation models of the ice sheet bed. Here, we demonstrate the potential of new high‐resolution (≤5 m) surface topography data (ArcticDEM) to provide enhanced insight into basal and englacial geometry and processes. Notable surface features, quantified via residual surface elevation, are observed coincident with documented subglacial channels, and new, smaller‐scale tributaries (<2,000 m in width) and valley‐like structures are clearly identified. Residual surface elevation also allows the extent of basal ice units to be mapped, which in conjunction with radar data indicate that they act as “false bottoms,” likely due to a rheological contrast in the ice column. Plain Language Summary Newly available high‐resolution (≤5m) surface elevationmaps of the Greenland Ice Sheet present a useful lens for examining and exploring the subglacial landscape, as well as the physical processes operating subglacially and englacially. Where radar data, which measure the subsurface geometry and properties, are sparse, we show how surface expressions can be used to enable effective interpolation between sets of bed data, allowing enhanced appreciation of ice sheet processes and boundary conditions. We also show that a subset of surface expressions originate from englacial slip surfaces or “false bottoms,” allowing the extrapolation of the 2‐D areal/horizontal extent of these features, not previously possible from radar flight lines alone.